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Jorge Rangel
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Android developer
Android developer

919 followers
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Tiny, Lens-Free Camera Could Hide in Clothes, Glasses. Surprised? It's sometimes called "Brin's Corollary to Moore's Law... the cams get smaller, faster, cheaper, better, more numerous and mobile with every passing day. Light is spreading everywhere and you will not evade it... but you might USE it to stay free and safe, if citizens learn to look back at power. See The Transparent Society: Will Technology Make Us Choose Between Privacy and Freedom?

https://www.livescience.com/59642-ultrathin-tiny-lens-free-camera.html


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Today we are pleased to announce the release of MobileNets, a family of mobile-first computer vision models for TensorFlow, designed to effectively maximize accuracy while being mindful of the restricted resources for an on-device or embedded application. MobileNets are small, low-latency, low-power models parameterized to meet the resource constraints of a variety of use cases. 

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The (Easter) holiday is a quasicrystal in time, rather than in space
– Ian Stewart, Mathematical Recreations, Scientific American, March 2001.

The clock (pictured below) in Notre-Dame-de-Strasbourg Cathedral, in Alsace, France was (most recently) built in 1843. An article by Bryan Hayes, for Sciences in 1999, mentions that there is a gear in the astronomical train of the clock that makes one rotation every 2,500 years, and that furthermore, the clock features a celestial globe that makes one rotation about an axis showing the precession of the Equinoxes only once every 25,000 years (the article was on Y2K compliance, and on how the Strasbourg clock is Y2K compliant with a vengeance).

However, this is not the most impressive feature of the clock. That would be the computus, which is a mechanical mechanism for calculating the date of Easter. There are only a handful of such devices in the world, because the calculations are so complex. The Strasbourg clock appears to be built to be theoretically correct until the year 10,000 AD (the year indication goes to 9,999 and Schwilgué is supposed to have helpfully suggested that in 10,000, someone might paint in a "1" to the left of the year window). However, if the computus follows a 10,000 year cycle, it will output the incorrect date for Easter in 11,999.

Here is a long, fascinating article about the difficulties of calculating the date of Easter in a mechanical clock.

Calculating the date of Easter didn't used to be quite so complicated. The rule according to the Julian calendar was fairly straightforward. A full cycle of full moon dates was thought to follow a 19 year cycle (the so-called Metonic cycle, which you might remember from our coverage of the Vacheron ultra-complication 57260) consisting of 235 lunar months. A fully cycle of the Julian calendar was 76 years (after four Metonic cycles – 19 x 4 = 76 – a full leap year cycle was completed also). Easter dates repeated, in the Julian calendar, every 536 years – as Ian Stewart points out in his 2001 Scientific American article on the subject, the mathematical principle is that, "532 is the lowest common multiple of 76 (the Julian calendar’s cycle) and 7 (the cycle of days in the week)." As we all know, though, the Julian calendar did not adequately correct for the actual time of the Earth's orbit around the Sun vs. the number of days in the calendar, and gradually it drifted badly out of sync with the seasons.

Then Pope Gregory XIII came along.
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With the new calendar came a new procedure for calculating the date of Easter. Each year would be assigned a number called the Epact – this was the age of the Moon on January 1 (the number could be anywhere from 1 to 29). In addition, each year was given a letter corresponding to the date of the first Sunday in January (A-G). These "Dominical Letters" (Leap Years get two) plus the Epact for that year, plus the Golden number (where you are in the Metonic cycle) are the raw material used to calculate the date of Easter. These are just the basics – in order to keep the ecclesiastical Moon and Equinox reasonably aligned to the astronomical ones, periodic adjustments have to be made which make the actual calculation much more complicated.

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